When a person outwardly presents as androgynous, there are two cases to consider:
- They intentionally present as androgynous, and may not (yet) be comfortable discussing/revealing their anatomy with you
- He/she hasThey have a naturally androgynous appearance, and may be embarrassed to be mistaken for a different sex
In the first case, your partner is aware of the need to resolve this issue before an awkward reveal in the bedroom. If you ask them outright, they probably won't be upset by the question, but may be uncomfortable answering. If that's the case, express support and wait until they are ready to have that conversation.
In the latter case, any attempt to ask outright may be extremely embarrassing and/or offensive to him/herthem. Invite him/herthem to participate in an activity that would necessarily reveal his/hertheir sex innocuously, such as going to a beach or pool, or to dress up for a fancy dinner.